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"And I think the fact that she was prepared to recognise the importance of the Irish language; that she was prepared to stand in a very dignified way to honour those patriots who struggled in 1916 to bring about a free and independent 32-county Irish Republic, that made an impact upon me.

"So that's an issue that I will ponder and I wouldn't rule anything out."

Sinn Fein did not take part in any of the main ceremonies when the Queen made her first visit to the Republic last spring.

However, last September, during the Irish presidential election, McGuinness said, that if he were elected president, he would meet all heads of state "without exception."

McGuinness was interviewed for the BBC's Inside Politics programme on Sunday.